The rings are made from polymers and the chemical reaction that creates them is similar to others that create polymer chains. But the new reaction solely makes rings, ones tailored to perform specific functions. The chemists report constructing polymer rings of a specific size and binding them to charged sodium atoms - a first step in a long road that could lead to applications in medicine.

Polymer chains are already often used in drug delivery, pointed out Malcolm Chisholm, Distinguished Professor of Mathematical and Physical Sciences and professor of chemistry at Ohio State. "The rings could encapsulate certain molecules, transport them somewhere, and release them at a specific time," he said.

The kind of ring molecules grown in this study, known as depsipeptides, are similar to some natural compounds produced by micro-organisms that are employed as antibiotics, such as valinomycin. "This project is really just beginning, and so there won't be any immediate applications. But there could be potential for future applications in medicine, because these molecules can be varied to perform specific functions," Chisholm said. A catalyst reacts with a single ring-shaped molecule, and multiplies it many times over, spawning rings of many different sizes. Chisholm likened the process to a child blowing a cascade of bubbles.

The rings form, break apart, and reform, until the chemists introduce a compound that specifically binds with one size ring in particular, and removes it from the mix. Then all the other rings assume the size and shape of the ring that was removed. "It's as if all the bubbles in the end collapse to that one particular bubble you were looking for," he said.

While there are other methods for making polymer rings and chains, this is the only one that solely makes rings. It's also the only one for which the catalyst is reusable indefinitely, which Chisholm counts as a significant advantage.